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2. |
- Ostrovskis, A., et al.
(author)
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240/160 Gbaud OOK Silicon Photonics MZM/RRM Transmitters for Short-Reach Applications
- 2023
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In: IEEE International Conference on Group IV Photonics GFP. - : IEEE Computer Society. - 9781665486552
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Conference paper (peer-reviewed)abstract
- We demonstrate a record 240 Gbaud on-off keying, 150 Gbaud 4-level pulse amplitude modulation, and 100 Gbaud 6-level pulse amplitude modulation SiP MZM-based transmitter with performance below the 6.25% overhead HD-FEC threshold. We also show a 160 Gbaud on-off keying SiP RRM-based transmitter.
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3. |
- Ozolins, Oskars, et al.
(author)
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100 GHz EML for high speed optical interconnect applications
- 2016
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In: European Conference on Optical Communication (ECOC). - : Institute of Electrical and Electronics Engineers Inc.. - 9783800742745 ; , s. 127-129
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Conference paper (peer-reviewed)abstract
- We report on a 116 Gbit/s OOK, 4PAM and 105 Gbit/s 8PAM optical transmitter using InP-based integrated EML for interconnect applications with up to 30 dB static extinction ratio and over 100 GHz 3 dB bandwidth with 2 dB ripple.
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4. |
- Pilotto, Francesca, et al.
(author)
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Meta-analysis of multidecadal biodiversity trends in Europe
- 2020
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 11:1
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Journal article (peer-reviewed)abstract
- Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15-91 years) collected across Europe, using a comprehensive dataset comprising ~6,200 marine, freshwater and terrestrial taxa. We test whether (i) local long-term biodiversity trends are consistent among biogeoregions, realms and taxonomic groups, and (ii) changes in biodiversity correlate with regional climate and local conditions. Our results reveal that local trends of abundance, richness and diversity differ among biogeoregions, realms and taxonomic groups, demonstrating that biodiversity changes at local scale are often complex and cannot be easily generalized. However, we find increases in richness and abundance with increasing temperature and naturalness as well as a clear spatial pattern in changes in community composition (i.e. temporal taxonomic turnover) in most biogeoregions of Northern and Eastern Europe. The global biodiversity decline might conceal complex local and group-specific trends. Here the authors report a quantitative synthesis of longterm biodiversity trends across Europe, showing how, despite overall increase in biodiversity metric and stability in abundance, trends differ between regions, ecosystem types, and taxa.
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5. |
- Udalcovs, Aleksejs, et al.
(author)
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An Insight into the Total Cost of Ownership of 5G Fronthauling
- 2018
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In: 20th International Conference on Transparent Optical Networks, ICTON 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538666050
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Conference paper (peer-reviewed)abstract
- This paper provides an assessment of the total cost of ownership (TCO) of a number of 5G fronthauling solutions based on digital and analog radio-over-fiber (RoF) architectures in cloud radio access network (C-RAN). We computed the capital and operational expenditures (CAPEX, OPEX) in the case of an optical fiber aggregation network based on a ring topology. Three different RoF architectures were considered: intermediate frequency analog RoF (IF-A-RoF), digital signal processing assisted analog RoF (DSP-A-RoF), and digital RoF (D-RoF) based on the common public radio interface (CPRI). A greenfield scenario considering both fiber deployment and fiber leasing was analyzed. The results presented in the paper show how the TCO changes with the number of aggregated carriers for the considered RoF architectures and fiber deployment strategy. They also reveal the impact that each cost category has on the overall CAPEX and OPEX value.
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6. |
- Al-Awis, S. N., et al.
(author)
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Phenomenological formula for modelling of physical layer impairments in elastic optical networks
- 2015
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In: Asia Communications and Photonics Conference, ACPC 2015. - Washington, D.C. : OSA. - 9781943580064
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Conference paper (peer-reviewed)abstract
- An empirical modelling technique is introduced to estimate impact of physical layer impairments in elastic optical networks, which can be used to evaluate transmission quality. The model has been verified experimentally with accuracy beyond (97.3%).
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7. |
- Cronqvist, S.E, et al.
(author)
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Psychic Changes following Myelography with Metrizamide and Iohexol : A comparative investigation with psychologic tests
- 1984
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In: Acta Radiologica Diagnosis. - 0567-8056. ; 25:5, s. 369-373
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Journal article (peer-reviewed)abstract
- Based upon the results of repeated psychologic tests, psychic impairment following myelography has been studied in 60 patients. Thirty of these had lumbar myelography with metrizamide and 30 with iohexol. Psychic impairment was noted in both groups, although with a higher frequency and much more marked in the group which had metrizamide myelography. For this type of examination iohexol is thus to be recommended.
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8. |
- CRONQVIST, S. E., et al.
(author)
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Psychologic Tests in the Evaluation of Psychic Changes after Myelography with Metrizamide
- 1984
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In: ; , s. 257-260
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Conference paper (other academic/artistic)abstract
- The possibility of using psychologic tests to demonstrate psychic changes following myelography with metrizamide was investigated in 15 patients. The tests were made before and after the examination. The results revealed psychic changes of cognitive nature to occur both at 6 and at 24 hours after myelography. Of the tests used determination of the reaction time gave most significant results. Subjectively the patients considered themselves better 24 hours after the examination than after 6 hours. This was not confirmed from the test results—an observation indicating the sensitivity of the test instruments used. Thus, these appear to be well suited to study cognitive changes caused by the contrast media used in this particular type of examination. Since the tests are repeatedly performed, the effect of habituation and of learning cannot be avoided. However, when applied in groups of patients, in whom the effects of different contrast media are compared, the disadvantages of these specific effects can be neglected.
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9. |
- Dely, H., et al.
(author)
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High bitrate data transmission in the 8-14 µm atmospheric window using an external Stark-effect modulator with digital equalization
- 2023
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In: Optics Express. - : Optica Publishing Group (formerly OSA). - 1094-4087. ; 31:5, s. 7259-7264
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Journal article (peer-reviewed)abstract
- High bitrate mid-infrared links using simple (NRZ) and multi-level (PAM-4) data coding schemes have been realized in the 8 µm to 14 µm atmospheric transparency window. The free space optics system is composed of unipolar quantum optoelectronic devices, namely a continuous wave quantum cascade laser, an external Stark-effect modulator and a quantum cascade detector, all operating at room-temperature. Pre- and post-processing are implemented to get enhanced bitrates, especially for PAM-4 where inter-symbol interference and noise are particularly detrimental to symbol demodulation. By exploiting these equalization procedures, our system, with a full frequency cutoff of 2 GHz, has reached transmission bitrates of 12 Gbit/s NRZ and 11 Gbit/s PAM-4 fulfilling the 6.25 % overhead hard-decision forward error correction threshold, limited only by the low signal-to-noise ratio of our detector.
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10. |
- Grimvall, Göran, et al.
(author)
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Lattice instabilities in metallic elements
- 2012
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In: Reviews of Modern Physics. - 0034-6861 .- 1539-0756. ; 84:2, s. 945-986
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Journal article (peer-reviewed)abstract
- Most metallic elements have a crystal structure that is either body-centered cubic (bcc), face-centered close packed, or hexagonal close packed. If the bcc lattice is the thermodynamically most stable structure, the close-packed structures usually are dynamically unstable, i.e., have elastic constants violating the Born stability conditions or, more generally, have phonons with imaginary frequencies. Conversely, the bcc lattice tends to be dynamically unstable if the equilibrium structure is close packed. This striking regularity essentially went unnoticed until ab initio total-energy calculations in the 1990s became accurate enough to model dynamical properties of solids in hypothetical lattice structures. After a review of stability criteria, thermodynamic functions in the vicinity of an instability, Bain paths, and how instabilities may arise or disappear when pressure, temperature, and/or chemical composition is varied are discussed. The role of dynamical instabilities in the ideal strength of solids and in metallurgical phase diagrams is then considered, and comments are made on amorphization, melting, and low-dimensional systems. The review concludes with extensive references to theoretical work on the stability properties of metallic elements.
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14. |
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15. |
- Marinins, Aleksandrs, 1988-, et al.
(author)
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Free carrier absorption modulation in polymer waveguides doped with Si nanocrystals
-
Other publication (other academic/artistic)abstract
- This work demonstrates all-optical intensity modulation in integrated optical polymer waveguides doped with Si nanocrystals. The modulation here is based on free carrier absorption of 1550 nm probe signal in Si nanocrystals with excited carriers. Optical 405 nm pump was used to increase free carrier concentration. By applying pulsed pump excitation, -1.55 dB deep intensity modulation was achieved in 5 mm long waveguides. The modulation bandwidth is limited to few kHz due to excited carrier relaxation time (τ ~ 100 μs). Demonstrated all-optical reconfigurable polymer waveguides are a promising potential alternative to thermo-optical switches.
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16. |
- Mucci, Nadia, et al.
(author)
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Genetic diversity and landscape genetic structure of otter (Lutra lutra) populations in Europe
- 2010
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In: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 11:2, s. 583-599
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Journal article (peer-reviewed)abstract
- Eurasian otter populations strongly declined and partially disappeared due to global and local causes (habitat destruction, water pollution, human persecution) in parts of their continental range. Conservation strategies, based on reintroduction projects or restoration of dispersal corridors, should rely on sound knowledge of the historical or recent consequences of population genetic structuring. Here we present the results of a survey performed on 616 samples, collected from 19 European countries, genotyped at the mtDNA control-region and 11 autosomal microsatellites. The mtDNA variability was low (nucleotide diversity = 0.0014; average number of pairwise differences = 2.25), suggesting that extant otter mtDNA lineages originated recently. A star-shaped mtDNA network did not allow outlining any phylogeographic inference. Microsatellites were only moderately variable (H (o) = 0.50; H (e) = 0.58, on average across populations), the average allele number was low (observed A (o) = 4.9, range 2.5-6.8; effective A (e) = 2.8; range 1.6-3.7), suggesting small historical effective population size. Extant otters likely originated from the expansion of a single refugial population. Bayesian clustering and landscape genetic analyses however indicate that local populations are genetically differentiated, perhaps as consequence of post-glacial demographic fluctuations and recent isolation. These results delineate a framework that should be used for implementing conservation programs in Europe, particularly if they are based on the reintroduction of wild or captive-reproduced otters.
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17. |
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18. |
- Ostrovskis, A., et al.
(author)
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106.25 Gbaud On-Off Keying and Pulse Amplitude Modulation Links Supporting Next Generation Ethernet on Single Lambda
- 2024
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In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 42:4, s. 1272-
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Journal article (peer-reviewed)abstract
- Development of Data Center based computing technology require energy efficient high-speed transmission links. This leads to optical amplification-free intensity modulation and direct detection (IM/DD) systems with low complexity equalization compliant with IEEE standardized electrical interfaces. Switching from on-off keying to multi-level pulse amplitude modulation would allow to reduce lane count for next generation Ethernet interfaces. We characterize 106.25 Gbaud on-off keying, 4-level and 6-level pulse amplitude modulation links using two integrated transmitters: O-band directly modulated laser and C-band externally modulated laser. Simple feed forward or decision feedback equalizer is used. We demonstrate 106.25 Gbaud on-off keying links operating without forward error correction for both transmitters. We also show 106.25 Gbaud 4-level and 6-level pulse amplitude modulation links with performance below 6.25% overhead hard-decision forward error threshold of 4.5×10-3. Furthermore, for EML-based transmitter we achieve 106.25 Gbaud 4-level pulse amplitude modulation performance below KP-FEC threshold of 2.2×10-4. That shows that we can use optics to support (2x)100 Gbps Ethernet on single lambda at expense of simple forward error correction.
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19. |
- Ozolins, Oskars, et al.
(author)
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100 Gbaud PAM4 link without EDFA and post-equalization for optical interconnects
- 2019
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In: IET Conference Publications. - : Institution of Engineering and Technology (IET). ; 2019:CP765
-
Conference paper (peer-reviewed)abstract
- We show 100 Gbaud PAM4 400 meters link with performance below the 7% HD-FEC limit of 5x10-3 without optical amplification and post-equalization. We also show 300 Gbps PAM8 line rate transmission over 400 meters of SSMF in C-band.
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20. |
- Ozolins, O, et al.
(author)
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High-speed optical interconnects with integrated externally modulated laser
- 2017
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In: Transparent Optical Networks (ICTON), 2017 19th International Conference on. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538608593 ; , s. 1-1
-
Conference paper (peer-reviewed)abstract
- The cloud services together with the huge size datasets are driving demand for bandwidth in datacenters [1]. The 400 Gbps client-side links are demanding cost efficient solution: to reduce the number of lanes and increase the bandwidth for a single lane. The intensity modulation and direct-detection systems together with integrated semiconductor lasers and modulators appear as promising solution in four optical lanes at 100G since it reduces complexity, power consumption and costs [2]. However, it requires silicon and InP opto-electronic components with more than 70 GHz bandwidth [3]. In this talk, we report on a cost-efficient integrated externally modulated laser (EML) with high bandwidth for record high-speed intensity modulation and direct detection system demonstration with up to 100G OOK, PAM4/8 and duobinary signaling, as well as analog modulations e.g. DMT, paving the way for high speed multilevel modulation formats [4–6]. Related techniques including digital signal processing algorithms for timing recovery, adaptive/static equalization are also discussed in terms of practical implementation and complexity. In addition, techniques constructively using time domain super-Nyquist image induced aliasing for mitigating modulator driver nonlinearity for high speed DMT transmission will be presented [6], [7].
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22. |
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23. |
- Pang, Xiaodan, Dr., et al.
(author)
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High-speed short reach optical communications : Technological options and challenges
- 2020
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In: Optics InfoBase Conference Papers. - : Optica Publishing Group.
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Conference paper (peer-reviewed)abstract
- We review the current trend in the research and development of short reach optical communications. Typical application scenarios with corresponding technological options are discussed, and an outlook on the challenges from different aspects are presented.
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25. |
- Salgals, Toms, et al.
(author)
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Silica Microsphere WGMR-Based Kerr-OFC Light Source and Its Application for High-Speed IM/DD Short-Reach Optical Interconnects
- 2022
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In: Applied Sciences. - : MDPI AG. - 2076-3417. ; 12:9, s. 4722-
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Journal article (peer-reviewed)abstract
- Kerr optical frequency combs (OFCs) based on silica microsphere whispering gallery mode resonator (WGMR) have various applications where they are used as a light source. For telecommunication purposes, WGMR-based Kerr-OFC comb generators can be physically realized using silica microsphere resonators and can be used to replace multiple laser arrays. In such a realization, these novel light sources have the potential to demonstrate an attractive solution for intra-datacenter interconnects (DCI). In this paper, we show an experimental demonstration of a silica microsphere WGMR-based Kerr OFC light source where newly generated 400 GHz spaced carriers together with powerful linear equalization techniques, such as a linear symbol-spaced adaptive decision-feedback equalizer (DFE) with feed-forward (FF) and feedback (FB) taps, provide an alternative to individual lasers ensuring low-cost and low-complexity IM/DD scheme for the transmission of NRZ-OOK modulated signals at data rates up to 50 Gbps/lambda over 2 km SMF link. Finally, we demonstrate a record 50 Gbps per lambda transmission of NRZ-OOK modulated signals with a novel silica microsphere WGMR-based Kerr-OFC as a light source operating in the optical C-band, surpassing the previously demonstrated data rate record by five times.
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26. |
- Udalcovs, A, et al.
(author)
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107.1-Gbps net-rate transmission over a joint 51km-fibre-and-10.7m-wireless link for terahertz radio access networks
- 2019
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In: 45th European Conference on Optical Communication, ECOC 2019. - : Institution of Engineering and Technology (IET). ; 2019:CP765
-
Conference paper (peer-reviewed)abstract
- 107.1 and 93.9-Gbps net-rate (gross-rate 133.9 and 101.3-Gbps) OFDM transmission on a 408-GHz carrier frequency is experimentally demonstrated over a joint fibre-wireless link, 51-km single-mode fibre and 10.7-m free-space, with bit-error-rates below the 20% soft- and 7% hard-decision FEC thresholds of 2.7×10-2 and 3.8×10-3, respectively.
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27. |
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28. |
- Zhang, Lu, et al.
(author)
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Lattice pilot aided DMT transmission for optical interconnects achieving 5.82-bits/Hz per lane
- 2019
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In: IET Conference Publications. - : Institution of Engineering and Technology. ; 2019:CP765
-
Conference paper (peer-reviewed)abstract
- We experimentally demonstrate 276-Gbps net rate 128QAM-DMT transmission at soft-FEC limit in an IM/DD system with a single C-band packaged EML, a DAC and a photo-detector, proposing a lattice pilot algorithm for channel equalization with only 1% overhead reaching spectral efficiency of 5.82-bits/Hz per lane.
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